apt-get install build-essential
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
build-essential : Depends: g++ (>= 4:4.4.3) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Is there another repository where I can get build essential?

I'd skip it but the tutorial indicates there would be problems later on if I did.

@ubuntu:~# apt-get install g++
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
g++ : Depends: g++-4.5 (>= 4.5.2-1~) but it is not going to be installed
Depends: gcc-4.5 (>= 4.5.2-1~) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

@ubuntu:~# apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
root@ubuntu:~# apt-get install build-essential
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
build-essential : Depends: libc6-dev but it is not going to be installed or
libc-dev
Depends: g++ (>= 4:4.4.3) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

I'd rather not chase down all the dependencies because that seems like a lost cause.

#
# deb cdrom:[Ubuntu-Server 11.04 _Natty Narwhal_ - Release amd64 (20110426)]/ natty main restricted
#deb cdrom:[Ubuntu-Server 11.04 _Natty Narwhal_ - Release amd64 (20110426)]/ natty main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://de.archive.ubuntu.com/ubuntu/ natty main restricted
deb-src http://de.archive.ubuntu.com/ubuntu/ natty main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://de.archive.ubuntu.com/ubuntu/ natty-updates main restricted
deb-src http://de.archive.ubuntu.com/ubuntu/ natty-updates main restricted
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://de.archive.ubuntu.com/ubuntu/ natty universe
deb-src http://de.archive.ubuntu.com/ubuntu/ natty universe
deb http://de.archive.ubuntu.com/ubuntu/ natty-updates universe
deb-src http://de.archive.ubuntu.com/ubuntu/ natty-updates universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://de.archive.ubuntu.com/ubuntu/ natty multiverse
deb-src http://de.archive.ubuntu.com/ubuntu/ natty multiverse
deb http://de.archive.ubuntu.com/ubuntu/ natty-updates multiverse
deb-src http://de.archive.ubuntu.com/ubuntu/ natty-updates multiverse
## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://de.archive.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse
# deb-src http://de.archive.ubuntu.com/ubuntu/ natty-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu natty-security main restricted
deb-src http://security.ubuntu.com/ubuntu natty-security main restricted
deb http://security.ubuntu.com/ubuntu natty-security universe
deb-src http://security.ubuntu.com/ubuntu natty-security universe
deb http://security.ubuntu.com/ubuntu natty-security multiverse
deb-src http://security.ubuntu.com/ubuntu natty-security multiverse
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu natty partner
# deb-src http://archive.canonical.com/ubuntu natty partner
## Uncomment the following two lines to add software from Ubuntu's
## 'extras' repository.
## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
# deb http://extras.ubuntu.com/ubuntu natty main
# deb-src http://extras.ubuntu.com/ubuntu natty main

The only time I modified this file was when the tutorial called for it. I believe that was just uncommenting a few lines.

My previous experience in server setup is with the Rackspace cloud. Well I have several sites humming along on it, I cannot do e-mail on the cloud. Such is the motivation for having the server in my house.